This invention relates to the art of optically controlled data switching. A typical switch will have at least one input port and at least one output port although a single input port could be switched between output ports. Generally, an optical signal is sent through the input port and routed to the appropriate output port by the switch.
Optical switches are commonly used in optical fiber communication systems. In such systems they route digital information across optical fiber networks. Another area is optoelectronic interconnects. In this area, optical switches can be used as repeaters and transceivers as well as for switching in optic communications links. For example, optical switches can be used to automatically switch out faulty devices in a communications network.
Present optical switches require the optical signal to be converted from optical to electrical form to determine if switching is required. The entire signal can then be changed back to optical and sent on to the determined path. In some of the present technology, an entire separate electronic control network is necessary to convert the signal from optical to electrical and back again. The process of switching the signal from optical to electrical and back again takes a great deal of time, limiting the usefulness of optical switches. The process limits the data rate within the network to the time that is required for the electronics to carryout the process. It would be beneficial for the data signal to remain in optical form. Using a tap off of the incoming optical signal, this invention reaches for this goal. Only information directing the data needs to be converted to electrical form and this provides for routing without converting the data portion of the signal.
Previously, the ability to tap off a part of an optical signal has been used with waveguides in fiber optic lines to send a signal to many different receiving nodes by splitting the signal. The waveguide would tap off or split off a fraction of an amount of a signal and send the tapped off or split off signal to a receiving node. The fraction to be tapped off or split off would be determined by the number of nodes in the system. If there are only a few nodes, the signal would be considered "split". For example, if one desired to have the signal divided so that an equal division of the signal goes to each node and if there are five nodes, then twenty percent of the signal would be split off, so twenty percent of the signal could be sent to each of the five nodes. Where there are more than twenty nodes, the signal may be tapped off at five percent or smaller levels so that each node receiving such a signal would get only a small part thereof through the tap-off.
This tapping off ability is used in this invention to tap off a fraction of an input signal and use the tapped off signal to determine the switch setting while the remainder of the input signal remains in optical form. The tap off ability would be beneficial in switches in that data transfer or switching would be allowed without slowing to convert the data portion of the optical signal. Current optical switches do not use a tap off ability for such a function.
The preferred method to tap off signals is with the use of waveguides. An example of a known optical waveguide switch may be seen in U.S. Pat. No. 4,759,595.
The invention would be particularly useful in an optical crossbar of switches interconnecting a number of processors. The invention can be used to help eliminate the need for a global controller that is required for global communication in a crossbar. The crossbar can also process the switching in parallel to increase the bandwidth for information communications.